Fastening of treads to drive wheel of friction mine hoist

ABSTRACT

A tread for the drive wheel of a friction mine hoist has an annular array of plastic blocks place end-to-end in a retaining groove on the periphery of the wheel. Each block has a small wedge-shaped piece split lengthwise off one side well to one side of the material under the rope, i.e., the rope wear material. During assembly of the blocks on the wheel, the small piece is placed in the groove first, after which the large piece is driven lengthwise into place, narrowest end first, beside the small piece so as to wedge the two pieces in the groove as a complete block. The sides of the groove may be undercut at the bottom thereof, and the blocks formed with shoulders that are wedged into the grooves.

[ 51 Sept. 19, 1972 [54] FASTENING OF TREADS TO DRIVE WHEEL OF FRICTION MINE HOIST [72] Inventors: Peter De Hertel Eastcott; William Herbert Jackson, both of Peterborough, Ontario, Canada [73] Assignee: Canadian General Electric Company Limited, Toronto, Ontario, Canada [22] Filed: Jan. 29, 1971 [21] Appl. No.: 110,992

[30] Foreign Application Priority Data April 14, 1970 Canada ..80031 [52] US. Cl ..254/ 190, 74/2307 [51] Int. Cl. ..B66d 1/36 [58] Field of Search ..254/ 190; 74/230.7

FOREIGN PATENTS OR APPLICATIONS 9/1937 Germany, .7 4/ 25o3 9/1955 GreatBritain ..74/230.7 5/1960 Germany ..74/230.7

Primary Examiner-Evan C. Blunk Assistant ExaminerMerle F. Maflei Attorney-Raymond A. Eckersley, Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT A tread for the drive wheel of a friction mine hoist has an annular array of plastic blocks place end-to-end in a retaining groove on the periphery of the wheel. Each block has a small wedge-shaped piece split lengthwise off one side well to one side of the material under the rope, i.e., the rope wear material. During assembly of the blocks on the wheel, the small piece is placed in the groove first, after which the large piece is driven lengthwise into place, narrowest end first, beside the small piece so as to wedge the two pieces in the groove as a complete block. The sides of the groove may be undercut at the bottom thereof, and the blocks formed with shoulders that are wedged into the grooves.

1 Claim, 2 Drawing Figures PATENTED SEP 1 I973 3.692.280

' sum 1 or 2 IN VEN'TOR.

PETER DEH. EASTCOTT )YVILLIAM H. JACKSON Patent A ent @LMMR PNE'N'TEDsEmm 3,692,280

SHEET 2 (IF 2 INVENTOR. TER DEH. STCOTT LIAM H. J KS BY Patent Agent FASTENING F TREADS TO DRIVE WHEEL OF FRICTION MINE IIOIST either end of the wheel, and is driven by an electric motor for rotation in either direction. A friction tread on the periphery of the wheel causes the ropes to follow rotation of the wheel and in so doing raise or lower the conveyances according to the direction of rotation. The tread consists of one or more circular rows of plastic blocks placed end-to-end on the periphery of the wheel and fastened thereto.

As is well-known the tread and the wheel structure supporting it are subjected to extremely severe operating conditions in that they carry the full weight of the ropes, the conveyances and the load being hoisted while this weight is accelerated or decelerated. As a result, the tread blocks are made of a tough and durable plastic material, and these blocks are fastened to the wheel in such a way that they remain in place, retain their shape, are not unduly deformed by the ropes, and are not subjected to more than expected wear.

' Numerous ways are known for fastening the tread blocks to the wheel, including a truncated block split diagonally into two wedge-shaped pieces. These wedge pieces are inserted one at a time into a truncated groove and driven into place one block at a time. Split blocks facilitate the installation of a tread and eliminate most, if not all, of the removable clamping devices need for securing other tread block configurations. The split block of the prior art does, however, have one major disadvantage, and that is the plane of the split cuts angularly across the rope retaining grooves. This introduces another break in each block. Additional breaks are not considered good engineering practice because they may weaken the tread in the rope groove where strength is needed most.

This invention relates to a split block configuration which retains the facility of installation and yet avoids having the plane of the split cross the rope retaining groove. According to the invention each tread retaining groove on the wheel is of rectangular outline in cross section and is undercut on both sides at the rim. Each block has parallel sides conforming with the sides of the groove, and has a pair'of shoulders which fit into the undercuts. Its axial thickness is great enough that a small wedge shape portion can be removed from one side of the block without interfering with the material under the rope groove, i.e., the material which comes into contact with the rope as the tread wears. The smaller portion of each block can now be set into the groove and the larger portion driven home beside it to lock the block in place.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which FIG. 1 is a perspective view in quarter section of a drive wheel for a friction mine hoist; and

FIG. 2 is a view in cross section of one groove of the wheel showing a tread block in place.

In FIG. 1 there is shown a drive wheel 10 having a hub 11, a coaxial rim 12, and structural members 13, 14 and 15 for supporting the rim on the hub. The rim has a pair of annular end flanges 16 and 17 which reinforce the wheel structure and serve as braking surfaces. Its periphery is formed with four annular grooves 18, 19, 20 and 21. These grooves are alike; each one has a pair of parallel sides 22 and 23 lying in spaced planes normal to the axis of rotation of the wheel. Each groove is undercut on both sides at the rim as indicated at 24 and 25. In both illustrations each groove is shown as being defined by a pair of annular flanges 26 and 27 projecting radially outward from the rim.

FIG. 2 shows two blocks 30 and 31 of a circular array of blocks that constitute a tread in one of the grooves 18 to 21. These blocks are located end-to-end in the groove on the wheel. Each block is a solid piece of plastic material such as urethane or polyvinylchloride of an outline in cross section which'conforms with the contour of the groove and is eight to twelve inches in length. It has a rope groove 32 and a pair of shoulders 33 and 34 which fit into undercuts 24 and 25 respectively. Each block is split into two pieces 35 and 36 along plane 37 as shown for block 30 and 31 in FIG. 2. This plane begins at one end of the block some distance from side 22 of the tread retaining groove and ends at the other end of the block much nearer side 22 of the groove. It begins on a radial line located between the groove side and the rope wear path 38 of groove 32 well away from the wear path, diverges from the path as it progresses along the length of the block, and ends on a radial line very close to this same groove side. It is so located that ample tread material is left in the large piece 36 under groove 32 for rope wear and block strength.

Each block may be moulded from the plastic material in one piece and then cut in two along plane 37 by means of a bandsaw. To fit a block 30, 31 in a tread retaining groove, certain steps are followed. Plane 37 of the smaller piece 35 is lubricated with soap and water, and this piece is then placed in the groove against side 22 with its shoulder 33 in undercut 24 and its wider end abutting the blocks already in place. Following this, the larger piece 36 is lubricated with soap and water and then placed in the groove against side 23 with its narrower end pointing toward the open space between piece 35 and side 23 and its shoulder 34 in undercut 25. Finally, a driving force is applied to the large end of piece 36 for driving it into the space between side 23 and piece 35. An air hammer may be used to provide this driving force. The blocks are assembled one at a time in this way, except for the last block which must be placed in the groove in some other way and secured by some other means. They are driven one against the other, and are made large enough that they are squeezed between the walls of the groove and firmly held in the undercuts so as to produce a tread which for all practical purposes is a solid ring of plastic filling the groove and its undercuts.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a friction mine hoist, a drive wheel having at least one tread retaining groove in its periphery, said groove having sides lying in planes normal to the axis of rotation of the wheel and an undercut in each at the bottom of the groove; a tread retained in said groove dercuts, and a diagonal split adjacent one side of the block lengthwise thereof well away from said rope groove and the tread material in the path of wear for the rope, said split separating a wedge-shaped piece from said one side of the block for facilitating assembly of the block on the wheel.

I I i i 

1. In a friction mine hoist, a drive wheel having at least one treaD retaining groove in its periphery, said groove having sides lying in planes normal to the axis of rotation of the wheel and an undercut in each at the bottom of the groove; a tread retained in said groove comprising a plurality of elongated tread blocks placed end-to-end in said groove in a ring around the wheel; a rope groove in the periphery of said ring of tread blocks; each one of said blocks having the general shape of a parallelepiped with sides fitting against the sides and bottom of said groove and ends in planes containing said axis, a pair of shoulders fitting into said undercuts, and a diagonal split adjacent one side of the block lengthwise thereof well away from said rope groove and the tread material in the path of wear for the rope, said split separating a wedge-shaped piece from said one side of the block for facilitating assembly of the block on the wheel. 